FROM ARTHRITIS CARE & RESEARCH
Rheumatoid arthritis patients who underwent silicone metacarpophalangeal joint replacement maintained significant improvement in ulnar drift and extensor lag after 7 years of follow-up in the prospective, multicenter Silicone Arthroplasty in Rheumatoid Arthritis (SARA) study.
The silicone metacarpophalangeal joint arthroplasty (SMPA) group also showed significantly better metacarpophalangeal (MCP) joint arc of motion, as well as function, aesthetics, and satisfaction scores than did patients in the cohort who chose nonsurgical management.
Investigators led by Kevin C. Chung, MD , and his colleagues from the University of Michigan, Ann Arbor, conducted what they claim is the largest prospective cohort study yet of RA joint replacement surgery by following 170 patients with RA, 73 of whom had elected to undergo SMPA with a Swanson implant and 97 who chose nonsurgical management. Patients were selected because they had severe deformity at the MCP joints, based on their combined ulnar deviation and an extensor lag greater than or equal to 50 degrees on average for each finger.
The practice of replacing deformed MCP joints with a hinged silicone implant has been around for almost half a century, the investigators noted, but despite widespread use, there is a lack of high-quality surgical outcomes data for the procedure. The authors suggested that the scarcity of data may create a barrier for surgical referrals from rheumatologists and could account for the declining rate of surgical intervention for RA joint deformities.
The significant improvement in ulnar drift that occurred in patients who underwent SMPA versus no surgery remained even after adjustment for baseline severity, age, sex, and use of biologics. The adjustment was especially important because the nonsurgical group had better function at baseline, with significantly stronger grip and pinch strength, better Michigan Hand Questionnaire ( MHQ ) scores, and significantly better ulnar drift, extensor lag, and arc of motion than in the surgical group ( Arthritis Care Res. 2016 Oct 1. doi: 10.1002/acr.23105 ).
The nonsurgical group largely maintained its baseline functional state during the 7-year follow-up period except for a decline in pinch strength.
“When the SMPA cohort was compared with the non-SMPA cohort, the covariate-adjusted difference showed significant benefits associated with SMPA hand outcome as measured by the MHQ function, aesthetics, and satisfaction scores, with no measures showing significantly better outcomes for the non-SMPA group,” the researchers wrote. “Although the average treatment effect estimate (ATT estimate) showed a decline over time for the average benefit from SMPA in those treated, the function score benefit as shown by the ATT estimate remained significant at year 5.”
Patients in the nonsurgical group were also given the option to crossover and receive surgery after 1 year, which two did. Eleven patients in the surgical group also decided to undergo surgery on their other hand.
Researchers saw one mild and three moderate implant-related adverse events during the study, including one patient who experienced ulnar deviation and needed a new joint replacement, one who dislocated the implant of the little finger a few weeks after insertion, and one who experienced sepsis in the joints 6 years after insertion and needed replacements for two implants. The fracture incidence of about 10% fits into the mid-range of previously reported fracture rates with this implant.
The study experienced significant losses to follow-up, particularly in the surgical group in which 7-year data were only available for 43% of participants in this group. The authors suggested this could have been because the surgical patients achieved their goals and were less inclined to the follow-up visits.
The study was supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases. No conflicts of interest were declared.
